Well there are the reports of those who knew Mirai. The thing is Mirai went to Charlene in mid season 2007...At Junior Worlds Goldenskate praised Mirai for her technical skating skills.
Well, according to this article in early 2009, Mirai has continued working with Kuchiki for her jumps:
http://articles.latimes.com/2009/jan/22/sports/sp-elliott-figure-skating22
And it also seems from the article that the desire to train with a large team, including continuing with Kuchiki, comes in large part from Mirai and her family. Charlene says it takes this much to train teenager like Mirai, and maybe she needs even more. One might even say that the continued influence of Kuchiki may be what held Mirai back from improving on her jumps.
Here's an older article:
http://web.icenetwork.com/news/article.jsp?ymd=20080131&content_id=43284&vkey=ice_news
Apparently Mirai first went to Charlene for her footwork. And I do think that Mirai now has some of the best footwork among the top US skaters. Her footwork is actually a highlight in her exhibitions, whereas Caroline leaves out complicated footwork in all her exhibitions. This speaks to the difference their respective abilities and confidence wrt to this element. The difference is also amply apparent in their competitive programs. Caroline can really use some help to make her skate harder transitions better in her programs. I somehow forgot that Charlene got coaching from Colson. Since she chose to highlight Colson's influence on her own skating and coaching, I think this bodes well -- because Patrick's skating skills and work ethic mainly came from Colson not Don Laws.
This article details Mirai's training regime:
http://www.newsday.com/topic/cs-080125-mirai-nagasu-short-program-champion,0,1596351,full.story
Apparently she only trained two days with Wong, and usually when a skater goes to all these different coaches on different days, the decision is driven by the skater and family, not by the primary coach. It also sounds like Mirai was difficult as a student, and they probably had personality clashes. I can't imagine Mirai saying to Frank Carroll: I don't like your perfume (not that I can imagine Carroll wearing any

), I'm not coming near you today for instructions.
And from this article:
http://archives.chicagotribune.com/2009/jan/21/sports/chi-22-hersh-skatejan22
it sounds like Mirai simply didn't get enough consistent training. And she also sounds like she had a bit of a motivation and/or attitude problem (not wanting to get up early to train, or do homework).
So all in all, at least from all the published material, it is not at all clear to me that Mirai's problems this year had to do with Charlene's coaching abilities. Now, maybe Mirai was already skated fast and jumped high prior to going to Charlene, but I didn't know anything about her skating back then and can't find any concrete material online either.
Btw, I think it's pretty factual to call Caroline a workaholic and Mirai not as one. "Workholic" refers to amount of time for working, not the quality. It seems like Caroline skated a lot but didn't get the highest quality of coaching, or at least the kind of coaching she needed to improve. Whereas Mirai was not often available to be coached, at least by Wong, whether it was because she was training with other coaches on other days, or not wanting to get up, or not liking Wong's perfume or advice.